On WM_DESTROY the editor was getting freed, then it was used to obtain
a handle to the editor.  This patch moves it just before the editor is
freed within ME_DestroyEditor.

widl: Store the size of a pointer in a variable instead of hardcoding the value of the host compiler.

The exact type can depend on the size of the type in memory, and that
can vary depending on whether we are generating 32-bit or 64-bit code.